Title: Dual-task training in Parkinson's disease: scope and effectiveness
Other Titles: Dubbeltaaktraining bij Parkinson: mogelijkheden, beperkingen en effectiviteit
Authors: Strouwen, Carolien
Issue Date: 16-Dec-2015
Abstract: Due to dopamine loss in the basal ganglia, patients with Parkinson's disease (PD) have problems performing automatic tasks like walking. The capacity to perform tasks automatically can be evaluated by assessing dual-task (DT) performance, which is defined as "the simultaneous performance of two tasks with distinct goals". Under DT situations, people with PD show a larger deterioration of performance than age-matched healthy control subjects, since conscious attention needs to be given to the tasks performed. Up to now, it remains unclear whether DT performance in people with PD can be improved by training and whether training can be offered in a safe way without increasing fall risk. The purpose of this doctoral thesis was therefore to gain more insight into the scope and effectiveness of DT training in people with PD. The basis of this research project was the DUALITY trial, in which two centers (KU Leuven, Belgium and Radboud University Medical Center, Nijmegen) were involved.
In a first study, we examined whether DT motor and DT cognitive outcome measures could be used reliably in longitudinal studies in patients with PD. We included data from 62 patients who underwent two DT tests repeated after a 6 week interval. We found that DT gait outcomes, particularly DT gait velocity, showed an excellent reliability, while proportional DT interference measures were less stable. We also showed that a functional dual task, such as using a mobile phone while walking, was a reliable and ecologically valid task with the potential to be used in the clinic.
In a second study, we determined which factors contributed to DT motor and DT cognitive performance in different types of dual tasks. In this analysis all patients participating in the DUALITY trial took part (N = 121). As expected, both motor and cognitive factors played a significant role in the determination of DT performance. We found that single-task gait performance together with a test of verbal fluency and task switching contributed most to DT gait performance. Determining factors remained constant in different types of dual tasks, while additional factors emerged in the Mobile Phone and Stroop task. Single-task cognitive performance was the most important determinant of DT cognitive performance.
The third study provided a summary of the recent literature on the effects of DT interventions in PD and an overview on current concepts of DT interference. Different strategies for improving DT performance were proposed, based on studies in older adults. Current evidence was inconclusive on whether DT training was useful in PD. However, two types of training strategies theoretically provided the best option: integrated task training (IDT) would increase the efficiency of brain areas thought to play an executive role in combining two tasks, whereas consecutive task training (CTT) would increase task automaticity, resulting in a higher level of residual brain capacity. Therefore, in the fourth study, we compared the effectiveness and safety of these two different training strategies, following the experimental set-up of the DUALITY trial. In this trial, 121 patients with PD were recruited and randomized into one of the two training groups. The first training group practiced gait and cognitive tasks separately (consecutive), while the other training group practiced gait tasks in combination with cognitive tasks (integrated). Participants received six weeks of training, twice a week in the presence of a physiotherapist and twice a week unsupervised. Before the intervention, DT performance was tested twice before and after a six week control period (test 1 and test 2). Effects of training on DT performance were assessed immediately after the intervention (test 3) and after 12 weeks of follow-up (test 4). The primary outcome was DT gait velocity during the Stroop task, which was an untrained task. Both training strategies proved to be effective in improving DT gait outcomes after training and no differences between strategies could be found. Training did not only improve trained dual tasks, but effects also transferred to untrained tasks and were retained at 12-weeks of follow-up. A second important finding was that fall risk did not increase during and after DT training. Effects on DT cognitive outcomes however were less consistent.
In study five, we examined which factors determined DT training effects. Comparable to study 2, motor and cognitive factors, which were assessed at baseline, determined the training effects. Better DT performance before training related to less improvement after training, probably indicating that less room for improvement was available in these patients. Better cognitive performance on the ScopaCog related to larger effects from training, especially in the integrated task training group.
In conclusion, this thesis provided insight into general mechanisms of dual tasking in PD and also generated a better understanding into the specific mechanisms underlying DT training interventions in people with PD. We found that DT measures can be used reliably in people with PD and are mostly determined by single-task performance and a test of executive function. Both consecutive and integrated strategies of DT training can be used effectively and safely in a large sample of people with early to mid stage PD. The effects suggested that task automatization, as well as a degree of task integration is possible in this patient group. The findings of this thesis offer new avenues for further research into the concept of dual tasking and DT training in PD and offer a framework for implementing DT interventions in clinical practice.
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Research Group for Neuromotor Rehabilitation

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